This disclosure relates to lubricating engines using formulated lubricating oils to reduce wear and improve engine fuel efficiency. The formulated lubricating oils contain a lubricating oil base stock, at least one carbon nanomaterial dispersed therein, and at least one block copolymer present in an amount sufficient to stabilize the dispersion of carbon nanomaterial in the lubricating oil basestock. The dispersion of in carbon nanomaterials in the lubricating oil is stabilized by the block copolymer such that the lubricating oil exhibits desired antiwear performance and engine fuel efficiency.